Dual-lumen catheters have come into widespread use for extracorporeal blood purification procedures such as hemodialysis. Blood is withdrawn from the patient through one of the lumens of the catheter and supplied to a hemodialysis unit where the blood is purified, and the resulting purified blood is then returned to the patient through the other lumen of the catheter. Examples of such catheters are shown in U.S. Pat. Nos. 4,134,402; 4,583,968; 4,568,329 and 4,692,141.
At the present time most dual-lumen catheters used for hemodialysis are made of either polyurethane or silicone rubber. The polyurethane catheters are sufficiently rigid that they can be introduced into a patient's vein percutaneously, without surgery, but such catheters tend to be incompatible with by the human body when left in place for long periods of time (e.g., a month or more). The silicone catheters can be left in place indefinitely without allergic reactions or traumatic problems in most patients, but the initial insertion of such catheters usually requires surgical intervention; the soft, pliable, elastic properties of the silicone which contribute to its compatibility with the human body are the same properties that make it difficult or impossible to insert such catheters percutaneously into a patient's vein.